Kinematic Comparison of Youth Pitching Using Lighter Baseballs

Abstract

0933 Many youth sport programs, such as football and basketball, have reduced the weight and size of the ball to accommodate youth athletes. However, baseball continues to use the same 5-ounce, 9 inch size baseball for Little Leaguers and Big Leaguers alike. PURPOSE: To investigate the effect of a lighter baseball on kinematic values of youth league baseball pitchers (age range: 9–12 yr, height: 1.54 ± 0.09 m, mass: 44.36 ± 9.42 kg). METHODS: Thirty-four youth baseball pitchers were tested in an indoor biomechanics laboratory. Each subject completed ten pitches using the 5-ounce and ten pitches using the 4-ounce baseball. Reflective markers were attached bilaterally to the distal end of the mid-toe, lateral malleolus, lateral femoral epicondyle, greater trochanter, lateral tip of the acromion, and lateral humeral epicondyle. Reflective markers were also attached to the ulnar and radial styloid processes along with the distal end of the third metacarpal of the throwing arm and to the ulnar styloid process of the non-throwing arm. The pitching motions of each subject were quantified with a three-dimensional automatic digitizing system using six electronically synchro-nized cameras that transmitted pixel images of the reflective markers directly into a video processor. Sixteen kinematic (11 position and 5 velocity) parameters were calculated and compared while throwing the different weight baseballs using two separate, two-way mixed factorial repeated measures ANOVA (velocity by weight of ball and position by weight of ball). RESULTS: There were no significant differences shown in the 11 position parameters, yet 3 of the 5 velocity parameters did show significant differences. An increase in maximum elbow extension velocity, maximum internal rotation velocity, and ball velocity were reported for the lighter, 4-ounce baseball compared to the 5-ounce baseball. CONCLUSIONS: Greater angular velocities at the shoulder and elbow, along with greater ball velocity using the 4-ounce baseball suggest that the quality of the game may be improved while reducing the weight of the baseball for young athletes. Since there were no differences shown in the position parameters, the increase in angular velocities and ball velocity is achieved without loss of proper pitching mechanics.